Pumping device

ABSTRACT

A fluid pumping device for placing inside a casing extending into a drilling well in order to pump a fluid present in a lower zone of the casing and delivering it to an upper zone of the casing. The fluid pumping device comprises an assembly of cylindrical elements placed end to end, the cylindrical elements of this assembly comprising:
         a seal to cooperate with the casing to ensure a tight seal between the lower zone and the upper zone;   a hydraulic pump;   an electric motor for driving the hydraulic pump, lubricated by a hydraulic fluid; and   a compensator to balance the pressure of the hydraulic fluid lubricating the electric motor with the pressure of the fluid in the lower zone of the casing.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM TO PRIORITY

This application claims priority to French Patent Application No. 1,452,987 filed Apr. 3, 2014 and French Patent Application 1,456,483 filed Jul. 4, 2014, the disclosures of which are incorporated herein by reference and to which priority is claimed.

FIELD OF THE INVENTION

The present invention relates to a pumping apparatus able to pump fluid from the base of deep drilling wells, wherein these wells may have a depth of up to about 3000 m or more, and the fluids to be pumped may be water loaded with contaminants and pollutants.

BACKGROUND OF THE INVENTION

It is known to lower a hydroelectric pumping unit into a well, lined by at least one tube, wherein the electric motor of such unit is powered by means of an electric cable supplying energy from the surface.

It is also known to use what is called a transfer pump in order to pump aggressive fluids, petrol or polluted fluids, at high pressure.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a pumping device that takes up little space so that it can be placed inside a casing of small diameter, about 50 mm or less, and that is reliable and allows the delivery of fluid from the well at −3000 m or more up to the surface, the fluid being likely to be contaminated, polluted and of low viscosity.

To achieve this, according to one embodiment, the invention relates to a fluid pumping device intended to be placed inside a casing extending into a drilling well, in order to pump a fluid present in the lower zone of the casing and deliver it to an upper zone of the casing, the pumping device comprising an assembly of cylindrical elements placed end to end, the cylindrical elements of this assembly comprising:

-   -   a seal able to cooperate with the casing to ensure a tight seal         between the lower zone and the upper zone;     -   a hydraulic pump;     -   an electric motor for driving the hydraulic pump, lubricated by         a hydraulic fluid; and     -   a compensator able to balance the pressure of the hydraulic         fluid lubricating the electric motor with the pressure of the         fluid in the lower zone of the casing, i.e. the pressure in the         lower zone of the well.

Thus the electric motor driving the hydraulic pump is placed under a pressure equal to or slightly higher than that of the liquid to be pumped, such that the pumping device may be arranged down to depths of the order of −3000 m without harming the function of the electric motor.

According to one embodiment, the hydraulic pump comprises two symmetrical inclined plates each cooperating with a set of pistons able to be displaced axially on a rotational movement of the inclined plates.

According to another embodiment, the invention relates to a fluid pumping device intended to be placed inside a casing extending inside a drilling well, in order to pump a fluid present in the lower zone of the casing and delivering it to an upper zone of the casing, the pumping device comprising an assembly of cylindrical elements placed end to end, the assembly of cylindrical elements comprising:

-   -   an element anchoring the pumping device inside the casing;     -   a seal able to cooperate with the casing in order to ensure a         tight seal between the lower zone and the upper zone;     -   a transfer pump comprising mobile pumping elements each         cooperating with a suction pipeline able to communicate with the         lower zone, and with a delivery pipeline able to communicate         with the upper zone, in order to draw fluid from the suction         pipeline and deliver it to the delivery pipeline;     -   a hydraulic pump with a double slope cam comprising an internal         hydraulic fluid circuit, a double slope rotatable cam, and two         sets of pistons able to be displaced axially on a rotational         movement of the double slope cam, the two sets of axial pistons         extending axially on either side of the double slope cam; the         hydraulic pump being associated with the transfer pump such that         displacement of the axial pistons of the hydraulic pump causes a         pressurization of the hydraulic fluid which drives the pumping         elements of the transfer pump;     -   an electric motor driving the hydraulic pump able to drive the         double slope cam in rotation; and     -   a compensator able to balance the pressure of the fluid in the         lower zone of the casing and the pressure in the internal         hydraulic circuit of the hydraulic pump.

Such a pumping device is particularly suited for the proposed application. In particular, a transfer pump under high pressure by a hydraulic pump is particularly suitable for delivering a fluid likely to be loaded with contaminants and pollutants. Furthermore, such a hydraulic pump with double slope cam allows delivery at high pressure while taking up little space and having a long service life due to the balancing of the axial forces exerted on the double slope cam.

According to preferred embodiments, such a pumping device may comprise one or more of the following characteristics:

-   -   the double slope cam comprises two identical and symmetrical         inclined faces against that come to rest respectively one or the         other of the two sets of pistons arranged symmetrically on         either side of said double slope cam;     -   the pistons are hollow pistons that are each able to slide in a         cylinder, the hollow pistons being able to draw in hydraulic         fluid during a suction phase and deliver hydraulic fluid during         a delivery phase, each inclined face of the double slope cam         having an intake passage arranged so as to cooperate with the         pistons of one of the sets of pistons during their intake phase.         Such an arrangement guarantees that on each turn of the cam, the         pumping elements of the transfer pump are returned to their         initial position during the intake phase of the piston(s) that         drive them;     -   the pumping elements of the transfer pump are supports which are         each counter-held by a spring and each comprise a head resting         under the effect of the spring against a flexible membrane, each         of the supports being associated with a cylinder in which a         piston of the hydraulic pump slides so as to be displaced         against the spring when said support is subjected, via the         flexible membrane, to a pressure of the hydraulic fluid         delivered into said cylinder by the piston during its delivery         phase;     -   the double slope cam comprises a plurality of drillings arranged         in the mass of the double slope cam, the drillings being         arranged so as to cooperate with two hollow pistons arranged         axially on either side of the double slope cam during a delivery         phase, so as to connect the cylinders in which the two hollow         pistons slide through the double slope cam. In other words, once         suction has been applied, the hydraulic fluid is delivered to         the transfer stage by one or more flexible membrane and its         supports, through the drillings produced in the double slope cam         of the hydraulic pump. Such an arrangement allows for a simpler         and less bulky hydraulic pump;     -   the pistons each cooperate with one of the two inclined faces of         the double slope cam via a hollow stud, the diameter of each         stud being greater than the distance separating two adjacent         drillings. Therefore the diameter of the studs is dimensioned so         as to not allow delivered hydraulic fluid to escape;     -   the hydraulic pump has a housing comprising pipelines arranged         to bring the cylinders with which the pistons of one of the         piston sets cooperate, into communication with the cylinders         with which the pistons of the other of the piston sets         cooperate;     -   the hydraulic pump comprises a housing and the transfer pump         comprises an upper pumping stage and a lower pumping stage         extending respectively on either side of the housing of the         hydraulic pump, each of the upper and lower pumping stages         comprising pumping elements associated respectively with the one         and the other of the piston sets, the delivery pipelines of the         two pumping units opening into a common pipeline, and the         delivery pipelines of the lower pumping unit communicating with         the common pipeline via a pipeline arranged along the casing of         the hydraulic pump;     -   the compensator comprises:         -   a tube with an inner space communicating with the internal             hydraulic circuit of the hydraulic pump and equipped with a             base through which passes a drilling communicating with the             lower zone; and         -   a flexible separator or free piston counter-held by a spring             and receiving firstly the pressure predominating in the             drilling and secondly the pressure predominating in the             internal hydraulic circuit of the hydraulic pump;     -   the electric motor has a housing comprising firstly a cover         through which passes a bore communicating with the inner space         of the tube, and secondly a cap through which passes a bore         communicating with the internal hydraulic circuit of the         hydraulic pump;     -   the electric motor comprises a stator and a rotor carried by a         motor shaft, the cover being provided with a bearing carrying         one of the ends of the motor shaft, and the cap being provided         with a bearing carrying the other end of the motor shaft, the         motor shaft being connected to a shaft of the hydraulic pump         carrying the double slope cam;     -   the seal is a compressible seal and the anchoring element         comprises catches able to be spaced apart, the pumping device         comprising a control mechanism for the seal and the anchoring         element that is mobile between a released position and an         engaged position, in which firstly the control mechanism axially         compresses the seal such that when the pumping device is placed         inside the casing, the seal is pressed radially against the         inner wall of the casing, and secondly the control mechanism         exerts a force on the anchoring element spacing the catches         apart, such that when the pumping device is placed inside the         casing, the catches come to rest against the inner wall of the         casing. Then the pumping device may be lowered in the casing         without being obstructed by the friction of the seal and/or the         anchoring element against the inner wall of the casing. Also,         when the pumping device is arranged at the desired depth, a         common control device allows positioning of the seal and the         anchoring element in the engaged position. Alternatively, the         pumping device may also comprise two separate control mechanisms         to control the seal and the anchoring element;     -   the control mechanism is a hydraulic control mechanism and the         pumping device comprises a hydropneumatic accumulator and a         distributor connected to the hydropneumatic accumulator and to         the hydraulic control mechanism, the distributor comprising a         closed position in which communication between the         hydropneumatic accumulator and the hydraulic control mechanism         is interrupted, and an open position in which communication         between the hydropneumatic accumulator and the hydraulic control         mechanism is established, in order to move the control mechanism         between its released position and its engaged position;     -   the hydraulic control mechanism is provided with a return means         able to return the control mechanism to its released position,         and is connected to the distributor such that the latter is able         to move the control mechanism into its engaged position;     -   the hydraulic control mechanism is provided with a return means         able to return and hold the hydraulic control mechanism in its         engaged position, and is connected to the distributor such that         the latter is able to move the control mechanism into its         released position;     -   the control mechanism comprises a shaft carrying a guide piston         and a cylinder mounted slidably on the guide piston against a         spring;     -   the cylinder comprises a first moveable stop surface and the         shaft comprises a second fixed stop surface, the anchoring         element being a deformable liner mounted on the shaft between         the first stop surface and the second stop surface, the seal         being mounted on the shaft between the first stop surface and         the second stop surface, the control mechanism comprising an         intermediate element arranged between the seal and the anchoring         element, the intermediate element comprising a flat surface         facing the seal and a conical surface facing the deformable         liner such that when the first stop surface is moved in the         direction of the second stop surface, the flat surface of the         intermediate element compresses the seal and spaces the         deformable liner from the anchoring element such that its         catches engage against the inner wall of the casing.

According to another embodiment, the invention relates to a pumping device intended to be placed inside a casing extending into a drilling well, in order to pump a fluid present in a lower zone of the casing and deliver it to an upper zone of the casing, the pumping device comprising an assembly of cylindrical elements placed end to end, this assembly comprising:

-   -   a seal able to cooperate with the casing in order to ensure a         tight seal between the lower zone and the upper zone;     -   a hydraulic pump;     -   an electric pump driving the hydraulic pump, lubricated by a         hydraulic fluid; and     -   a compensator able to balance the pressure of the fluid in the         lower casing zone and the pressure of the hydraulic fluid         lubricating the electric motor,

wherein the seal is situated at the base of said assembly,

wherein the pressure compensator comprises a cylindrical chamber in which a free piston slides counterheld by a spring, said free piston being firstly in contact with the fluid to be pumped, and secondly in contact with the hydraulic fluid lubricating the electric motor, so as to balance the pressure of the hydraulic fluid and the pressure of the fluid to be pumped, and

wherein the hydraulic pump comprises two symmetrical and opposing inclined rotatable plates, and two sets of hollow axial pistons resting against two inclined plates and able to be displaced axially by the rotational movement of the two inclined plates, the axial hollow pistons being housed in cylindrical chambers able to communicate with the lower zone of the casing and cooperating with a delivery pipeline able to communicate with the upper zone of the casing, the hollow axial pistons being arranged to draw in the fluid of the cylindrical chambers and delivering it to the delivery pipeline on a rotational movement of the two inclined plates.

According to preferred embodiments, such a pumping device may comprise one or more of the following characteristics:

-   -   the pressure compensator, the hydraulic pump and the electric         motor are housed in a cylindrical envelope, the delivery         pipeline opening to the outside of the cylindrical envelope into         a space intended to be arranged between the casing and said         cylindrical envelope and able to communicate with the upper         zone.     -   the pressure compensator comprises a cylindrical tube defining         the cylindrical chamber in which the free piston slides, and         wherein the cylindrical chambers accommodating the hollow axial         pistons are able to communicate with the lower zone of the         casing via a cylindrical space lying between the tube of the         pressure compensator and the cylindrical envelope, said tube of         the pressure compensator being provided with drillings allowing         the fluid to be pumped to penetrate between the tube of the         pressure compensator and the cylindrical envelope;     -   the two inclined plates are fixed to a plate drive shaft, the         drive shaft comprising two ends each cooperating with a support         bearing of said drive shaft arranged in a housing, the device         comprising a hydraulic fluid housing space in which the pressure         is balanced by the pressure compensator, the hydraulic fluid         housing space including the housings of the support bearings of         the drive shaft and a drilled conduit in the drive shaft         connecting said bearing housings.     -   the electric motor comprises a stator and a motor shaft carrying         a rotor, the motor shaft being connected in rotation to the         plate drive shaft and comprising two ends each cooperating with         a support bearing of the motor shaft arranged in a housing, the         hydraulic fluid housing space including the housings of the         support bearings of the motor shaft and the housing of the         electric motor.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and further objectives, details, characteristics and advantages thereof will appear more clearly during the following description of a particular embodiment of the invention, which is given merely for illustration and without limitation, with reference to the attached drawings.

FIG. 1 is a longitudinal section view of an embodiment of the pumping device according to the present invention;

FIGS. 2 to 4 are three longitudinal section views of three embodiments of the hydraulic pump;

FIG. 5 is a plan view of one of the two inclined faces of the cam of the hydraulic pump;

FIGS. 6 to 9 are four longitudinal section views of the device comprising a seal and anchoring means;

FIG. 10 is a detail view illustrating the functioning of the transfer pump;

FIG. 11 is a longitudinal section view of the first half of the pumping device according to a second embodiment;

FIG. 12 is a longitudinal section view of the second half of the pumping device of FIG. 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a well P provided with a casing T, at the base of which is a lower zone F where is situated the fluid which must be pumped to the surface.

The pumping device is lowered to the base of the well in order to pump the fluid present in the lower zone F and deliver it to an upper zone G arranged above the pumping device, in order to conduct the fluid to the surface. To allow lowering of the pumping device to the base of the well, it is composed of an assembly of cylindrical elements placed end to end, of diameter slightly lower than that of the casing T, which is about 50 mm.

The pumping device comprises successively, from its lower end to its upper end, a compensator 1, an electric motor 2, a hydraulic pump 3 driven by the electric motor 2, a transfer pump 4, a seal 60 able to cooperate with the casing in order to ensure a tight seal between the lower zone F and the upper zone G, and an element 62 for anchoring the pumping device inside the casing T.

The compensator 1 allows a balance to be achieved between the pressure of the fluid to be pumped and the pressure in the internal hydraulic circuit of the hydraulic pump 3. The compensator 1 comprises a tube 10 with an inner space 17 communicating with the internal hydraulic circuit of the hydraulic pump 3, as will be explained below. The tube 10 is provided with a base 11 through which passes a drilling 12 communicating with the zone F containing the fluid to be pumped. Inside the tube 10 is a free piston 13, or a flexible separator such as a membrane separator for example, counterheld by a spring 14 and receiving firstly the pressure predominating in the drilling 12, and secondly the pressure of the internal hydraulic circuit of the hydraulic pump 3.

The other end of the tube 10 is provided with a linking piece 15 ensuring a tight joint between the tube 10 of the compensator 1 and the housing of the electric motor 2. A bore 16 passes through the linking piece 15 and communicates with the inner space of the housing of the electric motor 2.

According to one embodiment, the electric motor 2 is powered via an electric cable (not shown) lowered into the casing T and thus allowing powering of the motor from the surface. Alternatively, the pumping device may be provided with a battery for powering the electric motor 2.

The housing of the electric motor 2 comprises a cylindrical body 26, a cover 20 fixed to the linking piece 15 of the compensator 1, and a cap 27 ensuring the connection of the housing of the electric motor 2 to the hydraulic pump 3. The motor has a stator 25 and a rotor (not shown) carried by a motor shaft 23. The cover 20 supports a bearing 24 carrying one of the ends of the motor shaft 23, while the cap 27 supports a bearing 24 carrying the other end of the motor shaft 23.

The cover 20 has a bore 21 communicating with the bore 16 of the linking piece 15. The cap 27 also has a bore 28 communicating with the inner space of the housing of the hydraulic pump 3.

As a result, the inner space 17 of the tube 10 of the compensator 1 communicates with the inner space of the housing of the hydraulic pump 3 via the inner space of the housing of the electric motor 2. These spaces are filled with oil. Thus the internal hydraulic circuit of the hydraulic pump 3 is pressurized, via the free piston 13 of the compensator 1 or a compensation membrane, to the pressure of the fluid to be pumped present in the lower zone F or to a pressure slightly greater than this.

Also, the motor shaft 23 is linked to a shaft 30 of the hydraulic pump 3. The shaft 30 of the hydraulic pump 3 is guided in rotation by a bearing 38 supported by the housing of the hydraulic pump 3. The shaft 30 is integral with a double slope cam 31 which actuates the pistons 32.

FIGS. 2 to 4 illustrate in detail the hydraulic pump 3 and its relationship with the pumping elements of the transfer pump 4 according to three embodiments.

The shaft 30 of the pump 3 is integral with the double slope cam 31. This cam 31 has two identical and symmetrical inclined faces 31 a and 31 b, against which two identical and symmetrical sets of pistons 32 come to rest. The pistons 32 are thus driven in an axial translation movement on rotation of the double slope cam 31. A first set of pistons 32 is arranged above the double slope cam 31 double slope cam 31 and rests against the upper inclined face 31 a, and a second set of pistons 32 rests against the lower inclined face 3lb of the double slope cam 31. The first and second piston sets 32 are arranged symmetrically to each other relative to the plane of symmetry of the double slope cam 31. The forces exerted on the cam 31 by the pistons 32 are therefore equal and opposed. Such an arrangement allows balancing of the axial loads on either side of the double slope cam 31, and thus gives the hydraulic pump 3 a long service life. The heads of the pistons 32 rest against the inclined faces 31 a, 31 b via hydrostatically balanced studs 34.

Also, the hydraulic pump 3 comprises two barrels 39 which extend on either side of the double slope cam 31, in which the cylinders 391 are arranged and in which the pistons 32 slide. The pistons 32 are hollow and thus define a suction chamber.

The transfer pump 4 comprises pumping elements each consisting of a support 40 counterheld by a spring 41. The head of this support 40 rests against a sealed flexible membrane 42 under the effect of the springs 41. The flexible membrane 42 and the support 40 are subjected to the pressure predominating in the cylinder 391, such that a movement of the piston 32 in the cylinder 391 causes a displacement of the support 40. Thus the hydraulic fluid driven by the pistons 32 of the hydraulic pump 4 actuates the pumping elements of the transfer pump 4, which thus draws in and delivers the liquid from the well in balanced pressure with the delivery pressure of the hydraulic pump 3.

When the cam 31 is driven in rotation by the shaft 3, faces 31 a and 31 b of the cam 31 cause a reciprocating motion of the pistons 32, during which these draw in hydraulic fluid from the internal space 33 of the pump and deliver it towards the pumping elements of the transfer pump 4, and vice versa.

Thus when a piston 32 is in the delivery phase, the corresponding support 40 is displaced against the return force of the spring 41. However, when the piston 32 is in the intake phase, the spring 41 repels the support 40 in the return direction and returns the support 40 to its initial position.

Each of the inclined faces 31 a, 31 b of the double slope cam 31 has an arched groove, called an intake passage 36, shown on FIG. 5. The intake passages 36 are each arranged to cooperate with the pistons 32 of one of the sets of pistons 32 during an intake phase. Thus on each rotation of double slope cam 31, the cylinders 391 are again brought into communication with the inner space of the hydraulic pump 4. Such an arrangement is particularly advantageous in that it guarantees that, on each turn of the cam, the supports 40 are returned to their initial position.

Furthermore, we note on FIG. 2 that the pumping elements of the transfer pump 4 each communicate with an intermediate pipeline 72 that communicates firstly with an intake pipeline 440 and secondly with a delivery pipeline 430. The intake pipeline 440 communicates with the lower zone F containing the fluid to be pumped, and the delivery pipeline 430 communicates with the upper zone G. The intake pipeline 440 and the delivery pipeline 430 are each provided with a non-return valve 43, 44.

When a piston 32 is in the delivery phase, the support 40 is displaced against the return force of the spring 41, and the fluid contained in the intermediate pipeline 72 is delivered towards the delivery pipeline 430. However, when a piston 32 is in the suction phase, the support 40 is returned to its initial position by the spring 41, which causes suction of the fluid to be pumped from the intake pipeline 440 to the intermediate pipeline 72.

In the embodiment shown in FIG. 2, the transfer pump 4 comprises an upper pumping stage and a lower pumping stage arranged on either side of the housing of the hydraulic pump 3. The lower pumping stage comprises pumping elements which are associated with the cylinders 391 cooperating with the set of pistons 32 arranged below the double slope cam 31, whereas the upper pumping stage comprises pumping elements which are associated with the cylinders 391 cooperating with the set of pistons 32 arranged above the double slope cam 31. The delivery pipelines 430 of the lower pumping stage and those of the upper pumping stage open into a common pipeline 47. The delivery pipelines of the lower pumping stage communicate with the common pipeline 47 via a pipeline 45 arranged along the housing of the hydraulic pump 3. This embodiment therefore requires the fluid to pass via the pipeline 45 arranged along the housing of the hydraulic pump, which is difficult to achieve because of the small space available. Also, this embodiment requires two pumping stages each comprising a set of supports 40 and non-return valves 43, 44.

In the embodiment shown on FIG. 3, the hydraulic fluid delivered by the pistons 32 of the lower set of pistons is brought into communication via pipelines 35 with the delivery of the pistons 32 of the upper set of pistons. In other words, each of the cylinders 391 of the lower barrel 39 cooperates with its opposing cylinder 391 of the upper barrel 39. This means that only a single set of supports 40 with their associated non-return valves 43, 44 is required. This embodiment however, like the embodiment in FIG. 2, requires passages for the delivered fluid along the housing of the pump, namely pipelines 35.

FIG. 4 illustrates the preferred embodiment. In this embodiment, the double slope cam 31 comprises a plurality of drillings 37 provided in the mass of the double slope cam 31 and extending axially between the upper inclined face 31 a and the lower inclined face 31b. The drillings are arranged to cooperate with two opposing hollow pistons 32 when these are in the delivery phase. Then the opposing cylinders 391, extending on either side of the double slope cam 31, are connected through the double slope cam 31 and the hollow pistons 32 when said pistons 32 are in the delivery phase. In other words, the delivery of the pistons 32 situated on the lower side of the cam 31 takes place through the drillings 37 to join the delivery of the pistons 32 situated on the other side of the cam 31.

Such an embodiment eliminates the need to provide pipelines in the housing of the hydraulic pump 3, such as pipelines 45 or 35 of the embodiments of FIGS. 3 and 4, which is important in view of the small space available.

FIG. 5 is a front view of one or the other of the faces 31 a and 31 b of the double slope cam 31 of the embodiment in FIG. 4. As described above, faces 31 a, 31 b of the double slope cam 31 each comprise an intake passage 36 and a series of drillings 37. The diameter of each stud 34, creating the link between the head of pistons 32 and the double slope cam 31, is greater than the distance separating two adjacent drillings 37. Thus the diameter of the studs is dimensioned such that communication between two opposing studs 34 is never interrupted when they are in the delivery phase.

FIG. 10 is a cross-section of the transfer pump 4. As already described above, the pumping elements of the transfer pump consist of a support 40 counterheld by a spring 41, the head of which rests under the effect of the springs 41 against a flexible membrane 42, subjected to the pressure predominating in a cylinder of the hydraulic pump 3. Each support 40 is thus actuated by the pressure provided by a piston 32 of the hydraulic pump 3.

The fluid to be drawn in surrounds the body of the transfer pump 4 as indicated with reference 48. The body of the transfer pump 4 is therefore equipped with an intake pipeline, not shown in the cross-section view on FIG. 10, which opens at 48. The intake pipeline communicates with a chamber 49 provided with a non-return valve 44, said chamber 49 communicating via a pipeline 71 with an intermediate pipeline 72 arranged between the support 40 and a delivery pipeline (not shown) fitted with another non-return valve 43. The delivery pipeline communicates with zone G situated above the pumping device, i.e. with the fluid delivery zone. In one embodiment, the fluid from the well, drawn in by the transfer pump 4, is preferably filtered by a filter arranged in the intake pipeline.

As soon as the support 40 is repelled by the return spring 41 (intake phase of piston 32), the fluid from the well is drawn in by the non-return valve 44. As soon as the support 40 is repelled by the hydraulic fluid of the hydraulic pump 3 (delivery phase of the piston 32), the fluid of the well is delivered in balanced pressure with the hydraulic fluid through the delivery pipeline via the non-return valve 43.

Furthermore, the pumping device is also provided with an anchoring element 62, a seal 60, a mechanism 5 for controlling the seal 60 and the anchoring element 62, a hydropneumatic accumulator 57 and a distributor 58 which are shown integrated in the pumping device assembly on FIG. 1.

The seal 60 has a function essential for the operation of the pumping device, since it must separate the lower zone F containing the fluid to be pumped from the zone G into which the fluid is delivered. The seal 60 must also be able to tolerate a significant pressure difference between the lower zone F and the upper zone G, which may be as much as 300 bar.

The seal 60 is advantageously arranged close to the upper end of the pumping device.

The liquid to be pumped is therefore not only below the pumping device but also in the space between the casing T and the wall P of the well, and in the space lying between firstly the compensator 1, electric motor 2, hydraulic pump 3 and transfer pump 4, and secondly the inner wall of the casing T, such that the transfer pump 4 will extract the liquid to be delivered from the space surrounding it in order to deliver it into zone G.

Thus the various elements of the pumping device are not subjected to the high pressure predominating in the upper zone G. Therefore the housing of the electric motor 1 and the housing of the hydraulic pump 2 are not exposed to high pressures, so they may have smaller thicknesses in order to promote a heat exchange between the fluid to be pumped and the hydraulic fluid accommodated in the housing of the electric motor 2 and in the housing of the hydraulic pump 3. Moreover, this also offers greater freedom of design in the choice of materials constituting the housings of the electric motor 2 and the hydraulic pump 3.

In order to allow the delivery of the fluid from the transfer pump 4 to the upper zone G, the hydropneumatic accumulator 57 and the distributor 58 are accommodated in cylindrical housings provided with delivery pipelines 571, 578 which communicate with the delivery pipelines of the transfer pump 4. Furthermore, the control mechanism 5 for the seal 60 and the anchoring element 62 comprises a shaft 60 which is provided with a delivery pipeline 501 communicating with the delivery pipeline 578 and opening into the upper zone G.

The function of the control mechanism 5 of the seal 60 and the anchoring element 62, the hydropneumatic accumulator 57 and the distributor 58, will be described in detail in relation to FIGS. 6 to 9.

The seal 60 is a compressible seal. When the seal 60 is compressed radially as shown on FIGS. 7 and 9, the outer periphery of the seal 60 is pressed against the inner wall of the casing T so as to ensure a tight seal.

The anchoring element 62 is provided with catches 64 which are able to move apart so as to engage with the inner wall of the casing T in order to anchor the pumping device inside the casing T. The anchoring element 62 is able to tolerate the force generated by the pumping device multiplied by the delivery pressure of the pumping device. The anchoring element 62 must also ensure sufficient anchoring force to block the pumping device in rotation during operation.

FIGS. 6 and 7 illustrate a control mechanism 5 according to a first embodiment, while FIGS. 8 and 9 illustrate a control mechanism 5 according to a second embodiment.

The control mechanism 5 is able to be moved between a release position shown on FIGS. 6 and 8, in which the seal 60 and the anchoring element 62 do not cooperate with the inner wall of the casing, and an engagement position illustrated on FIGS. 7 and 9. In the engagement position, the control mechanism 5 firstly axially compresses the seal 60 such that its outer periphery is pressed against the inner wall of the casing T, and secondly spaces the catches 64 of the anchoring element 62 such that they engage with the inner wall of the casing T.

The control mechanism 5 comprises a shaft 50 carrying a guide piston 52. The control mechanism 5 also comprises a cylinder 54 mounted slidably on the shaft 50. For this, the cylinder 54 comprises an inner chamber which accommodates the guide piston 52 and a return spring 55. The inner chamber of the cylinder 54 is able to be pressurised so as to cause the cylinder 54 to slide against the return force of the spring 55.

The inner chamber of the cylinder 54 is linked to an energy reserve, here formed by a hydropneumatic accumulator 57. The hydropneumatic accumulator 57 is connected to the inner chamber of the cylinder 54 via a distributor 58. The distributor 58 has a closed position in which communication between the hydropneumatic accumulator 57 and the inner chamber of the cylinder 54 is cut, and an open position in which this communication is established. A pipeline 59 arranged in the shaft 50 brings the reserve of hydraulic fluid into communication with the inner chamber of the cylinder 54.

As shown on FIG. 7, in order to move the control mechanism 5 towards its engagement position, the cylinder 54 is moved in the direction of the upper zone G along the direction of arrow F.

Furthermore, the shaft 50 passes through the compressible seal 60 and the anchoring element 62. An intermediate element 61 is arranged between the compressible seal 60 and the anchoring element 62. The intermediate element 61 comprises firstly a flat surface coming to face the compressible seal 60, and secondly a conical surface coming to face the anchoring element 62. The intermediate element 61 is mounted sliding on the shaft 50. The compressible seal 60, the intermediate element 61 and the anchoring element 62 are arranged between a stop surface 502 carried by the cylinder 54 and a stop surface 53 carried by the shaft 50.

The anchoring element 62 comprises a deformable lining with a plurality of elements distributed around the shaft 50 and held by a hoop 63. At one of their ends, these elements surround the end of the conical piece 61 and at their other end they rest against the stop surface 53. The elements 62 may swivel around the hoop 63. The outer wall of the ends of the elements surrounding the conical piece 61 is provided with a catch 64.

The shaft 50 is also provided with a circular ring 50 a serving as a support surface for the intermediate element 61.

The function of the control mechanism 5 described is as follows.

When the accumulator 57 releases part of its energy reserve thanks to the distributor, it supplies the chamber of the cylinder 54 and the thrust surface of the guide piston 52, which leads to a relative axial movement between the cylinder 54 and the shaft 50. Because of this relative axial movement, the compressible seal 60 is compressed between the stop surface 502 of the cylinder 54 and the intermediate element 61. The intermediate element 61 and the anchoring element 62 are pressed against each other such that the pieces of the anchoring element 62 swiveling about the hoop 63 rise along the conical surface of the intermediate element 61, which presses their catches 64 against the inner wall of the casing T. Furthermore, the intermediate element 61 comes to stop against the ring 50 a of the shaft so as to allow compression of the seal 60. This compression has the effect of deforming the seal 60 and pressing it strongly against the inner wall of the casing T.

Therefore the following are achieved simultaneously: the desired tightness between the suction zone F of the fluid to be pumped and the delivery zone G of this fluid, and the anchoring of the pumping device inside the casing T.

FIGS. 8 and 9 show the reverse function of that in FIGS. 6 and 7. In fact in this embodiment, the spring 55 permanently holds the seal 60 crushed against the wall of the casing T and the catches 64 in engagement (FIG. 9). Then to move the control mechanism 5 to its released position, the distributor 58 is placed in its opening position so as to fill the inner chamber of the cylinder and move the cylinder 54 against the return force of the spring 55.

We note that although the seal 60, the anchoring element 62 and the control mechanism 5 are particularly suited for the pumping device described above, they may also be applied to any pumping device intended to be anchored tightly inside a casing.

With reference to FIGS. 11 and 12, a pumping device according to another embodiment will now be described.

As in the case of the embodiment described above, the pumping device is lowered to the base of the well in order to pump the fluid present in the lower zone F and deliver it to the upper zone G situated above the pumping device, in order to conduct said fluid to the surface. If the well has a depth of about 3000 m, the delivery pressure must be of the order of about 300 bar. As in the case above, the pumping device is composed of an assembly of cylindrical elements placed end to end, of a diameter slightly less than that of the casing T which is of the order of about 50 mm.

This pumping device comprises successively, from its lower end to its upper end: a seal 100, a pressure compensator 200, a hydraulic pump 300 and an electric motor 400. The compensator 200, pump 300 and motor 400 are housed in a cylindrical envelope 500.

The seal 100 has the function of separating the casing T into two zones, a low pressure zone and a high pressure zone. It is carried by a plug 101. The means by which the seal 100 is pressed against the wall of the casing T to ensure the tightness between the low pressure zone and the high pressure zone are not described or shown in relation to the second embodiment in FIGS. 11 and 12. Similarly, the element anchoring the pump device inside the casing T is not shown. As an example, the fluid pumping device according to this second embodiment may be provided with a seal, an anchoring element and a control mechanism for the seal and anchoring element which are substantially similar to those of the first embodiment.

The pressure compensator 200 comprises a plug 201 attached to the end of the cylindrical envelope 500 and screwed onto the plug 101. The pressure compensator 200 also comprises a tube 202 carried by the plug 201, so as to define a cylindrical chamber 202 a in which a free piston 203 slides counterheld by a spring 204. The fluid to be pumped present in the lower zone F arrives in chamber 202 a via the pipeline 210 which passes through the plugs 101 and 201. The other part 205 of the chamber 202 a is filled with hydraulic fluid and communicates with a chamber 206 provided in a cylindrical part 207, fixed inside the cylindrical envelope 500. Thus the free piston 203 is in contact firstly with the liquid to be pumped and secondly with a housing space of a hydraulic fluid, lubricating in particular the electric motor 400 for driving the hydraulic pump, as will be described below.

The hydraulic pump 300 comprises two inclined plates 300 a and 300 b keyed onto a shaft 302, against which the hollow axial pistons 301 a and 301 b rest. Plates 300 a and 300 b are symmetrical and have opposing slopes. When plates 300 a, 300 b are driven in rotation by the shaft 302, they oscillate in the cylindrical chambers 303 a and 303 b which communicate with each other.

The inclined faces of plates 300 a and 300 b cause a reciprocating motion of the pistons 301 a, 301 b, during which they draw fluid into the cylindrical chambers 303 a and 303 b and deliver it into the cylindrical space between the envelope 500 and the casing T via a delivery pipeline 308.

Hollow pistons 301 a and 301 b are held resting against plates 300 a, 300 b by springs 309 via studs 310. Plates 300 a, 300 b each comprise an intake passage with which the opposing hollow pistons 301 a, 301 b cooperate when in the suction phase. Thus the cylindrical chambers 303 a, 303 b are brought into communication with the interior of the hollow pistons 301 a, 301 b via the passage when said hollow pistons are in the suction phase. The hollow pistons 301 a, 301 b are housed in cylinders provided in a central barrel. The central barrel is arranged between two plates 300 a, 300 b. The cylinders of two opposing hollow pistons open into a common pipeline provided with a non-return valve 311.

Because the inclined plates 300 a and 300 b are symmetrical and have opposing slopes, pistons 301 a and 301 b have movements in opposite directions. Furthermore, hollow pistons 301 a, 301 b are arranged opposite each other such that the forces they create are balanced. The cylindrical chambers 303 a, 303 b communicate with zone F containing the fluid to be pumped via a cylindrical space between the tube 202 of the pressure compensator 200 and the cylindrical envelope 500. The cylindrical chambers 303 a, 303 b communicate with the cylindrical space between the tube 202 and the cylindrical envelope 500 via pipelines arranged in the support piece 314 of the bearing 304 of the drive shaft 302 of plates 300 a, 300 b and in the cylindrical part 207. The cylindrical space between tube 202 and the cylindrical envelope 500 communicates with the interior of tube 202 via a plurality of drillings 211 provided in the tube 202.

The drive shaft 302 for plates 300 a, 300 b is carried by two bearings 304 and 305 situated at its two ends. Bearings 304, 305 are arranged in housings provided in bearing support pieces 314, 315. A pipeline 306 passes through the entire length of the drive shaft 302 for the plates 300 a, 300 b.

The electric motor 400 has a stator and a motor shaft 401 carrying the rotor (not shown). The motor shaft 401 is carried at both ends by two bearings 402 a and 402 b and connected in rotation to shaft 302 of the hydraulic pump 300. In the embodiment shown, the electric motor 400 is electrically powered via a connection 403. Alternatively, the pumping device may be equipped with a battery for powering the electric motor 400.

The housing space of the hydraulic fluid, under a pressure slightly higher than the fluid to be pumped by the compensator 200, comprises the chamber 206 arranged in the cylindrical piece 207, the housings of bearings 304, 305 supporting the drive shaft 302, the housings of bearings 402 a, 402 b supporting the motor shaft 401 and the electric motor housing. In fact chamber 206 filled with hydraulic fluid communicates via drillings 208, 209 with the housing of bearing 304, and via the conduit 306 drilled in shaft 302 with the housing of bearing 305, which itself communicates with chamber 307 filled with hydraulic fluid. Said chamber 307 communicates with chamber 403 which communicates with the chamber of bearing 402 a. The spaces containing the windings of the motor 400 and its shaft 401 are filled with hydraulic fluid which also fills the housing of bearing 402 b.

Consequently, the hydraulic fluid lubricates the two bearings 304 and 305 of the hydraulic pump and the two bearings 402 a and 402 b of the motor 400. The space containing the hydraulic fluid is tightly separated from the space containing the fluid to be pumped, via the seals 312, 313.

The envelope 500 which houses all the elements 200, 300 and 400 has a diameter slightly smaller than that of the casing T: the cylindrical space between the envelope 500 and the casing T receives the fluid pumped by the pipeline 308. Furthermore, piece 404 carrying connection 403 also has a diameter slightly smaller than that of the casing T. As a result, the space between the envelope 500 and the casing T communicates with the high pressure delivery zone G of the pumped fluid. This means that said envelope 500 must be configured to be able to resist this high pressure.

The distribution of pressures in the pumping device according to the second embodiment of the invention is as follows: the volumes formed by the pressure compensator 200 and the chambers 303 a and 303 b of pump 300 are under low pressure; the cylindrical volume surrounding the envelope 500 housing the compensator 200, the pump 300 and the motor 400 is under high pressure; the volumes containing the bearings 304 and 305 of pump and 402 a and 402 b of the motor are under the hydraulic fluid pressure which is slightly higher than the low pressure because of spring 204.

The device functions as follows: when the motor 400 is powered via its connection 403, it drives the shaft 302 which drives the oscillating plates 300 a and 300 b, pistons 301 a and 301 b draws in the fluid to be pumped present in the chambers 303 a and 303 b, and delivers it at high pressure via pipeline 308 into the cylindrical space between the envelope 500 and the casing T, which space opens into zone G.

Although the invention has been described in connection with several particular embodiments, it is evident that it is in no way limited to these and comprises all technical equivalents of the means described and their combinations if these fall within the context of the invention.

Use of the verbs “contain”, “comprise” or “include” and their conjugate forms does not exclude the presence of forms or steps other than those listed in a claim. Use of the indefinite article “a” for an element does not, unless specified otherwise, exclude the presence of a plurality of such elements.

In the claims, any reference symbol in brackets should not be interpreted as a limitation of the claim. 

1. A fluid pumping device for placing inside a casing extending into a drilling well to pump a fluid from a lower zone of the casing to an upper zone of the casing, the pumping device comprising an assembly of cylindrical elements placed end to end, the cylindrical elements of this assembly comprising: a seal that cooperates with the casing to ensure a tight seal between the lower zone and the upper zone; a hydraulic pump; an electric motor lubricated by hydraulic fluid for driving the hydraulic pump; and a pressure compensator that balances the pressure of the hydraulic fluid lubricating the electric motor with the pressure of the fluid in the lower zone of the casing.
 2. The pumping device according to claim 1, wherein the seal is situated at the base of said assembly; the pressure compensator comprises a cylindrical chamber in which a free piston slides counterheld by a spring, said free piston being in contact with the fluid to be pumped and with the hydraulic fluid lubricating the electric motor, so as to balance the pressure of the fluid to be pumped and of the hydraulic fluid; and the hydraulic pump comprises two symmetrical and opposing inclined plates mobile in rotation, and two sets of hollow axial pistons resting against the two inclined plates, the hollow axial pistons being able to be displaced axially by the rotational movement of the two inclined plates, housed in cylindrical chambers able to communicate with the lower zone of the casing and cooperating with a delivery pipeline able to communicate with the upper zone of the casing, and arranged to draw in the fluid from the cylindrical chambers and deliver it to the delivery pipeline on a rotational movement of the two inclined plates.
 3. The pumping device according to claim 2, wherein the pressure compensator, the hydraulic pump and the electric motor are housed in a cylindrical envelope, and the delivery pipeline opens to the outside of the cylindrical envelope into a space between the casing and the cylindrical envelope.
 4. The pumping device according to claim 3, wherein the pressure compensator comprises a cylindrical tube defining the cylindrical chamber in which the free piston slides, and the cylindrical chambers accommodating the hollow axial pistons communicate with the lower zone of the casing via a cylindrical space lying between the tube of the pressure compensator and the cylindrical envelope, said tube of the pressure compensator comprising drillings allowing the fluid to be pumped to mix between the tube of the pressure compensator and the cylindrical envelope.
 5. The pumping device according to claim 2, wherein the two inclined plates are fixed to a plate drive shaft, the plate drive shaft comprising two ends each cooperating with support bearings arranged in housings, the pumping device comprising a hydraulic fluid housing space in which the pressure is balanced by the pressure compensator, the hydraulic fluid housing space comprising the support bearing housings of the drive shaft and a drilled conduit in the drive shaft connecting the support bearing housings.
 6. The pumping device according to claim 5, wherein the electric motor comprises a housing, a stator and a motor shaft carrying a rotor, the motor shaft being connected in rotation to the plate drive shaft and comprising two ends each cooperating with support bearings of the motor shaft arranged in housings, the hydraulic fluid housing space further comprising the support bearing housings of the motor shaft and the housing of the electric motor.
 7. The pumping device according to claim 1, further comprising: an element anchoring the pumping device inside the casing; and a transfer pump comprising mobile pumping elements, each cooperating with a suction pipeline that communicates with the lower zone, and with a delivery pipeline that communicates with the upper zone, in order to draw in fluid from the suction pipeline and delivering it to the delivery pipeline; wherein the hydraulic pump is a hydraulic pump with a double slope cam comprising an internal hydraulic fluid circuit, a double slope cam mobile in rotation, and two sets of pistons able to be displaced axially on a rotational movement of the double slope cam, the two sets of axial pistons extending axially on either side of the double slope cam; the hydraulic pump being associated with the transfer pump such that a displacement of the axial pistons of the hydraulic pump causes pressurization of the hydraulic fluid that drives the pumping elements of the transfer pump; wherein the electric motor driving the hydraulic pump drives the double slope cam in rotation; and wherein the pressure compensator balances the pressure of the fluid in the lower zone of the casing and the pressure in the internal hydraulic fluid circuit of the hydraulic pump.
 8. The pumping device according to claim 7, wherein the double slope cam comprises two identical and symmetrical inclined faces against which rest respectively one or the other of the two sets of axial pistons arranged symmetrically on either side of the double slope cam.
 9. The pumping device according to claim 8, wherein the axial pistons are hollow, each able to slide in a cylinder, the hollow axial pistons drawing in hydraulic fluid during a suction phase and delivering hydraulic fluid during a delivery phase, each inclined face of the double slope cam having an intake passage arranged so as to cooperate with at least one of the hollow axial pistons during the suction phase.
 10. The pumping device according to claim 9, wherein the pumping elements of the transfer pump are supports which are each counterheld by a spring and each comprise a head resting against a flexible membrane under the effect of the spring, each of the supports being associated with a cylinder in which a piston slides so as to be displaced against the spring when said support is subjected, via the flexible membrane, to a pressure of the hydraulic fluid delivered into said cylinder by the piston during the delivery phase.
 11. The pumping device according to claim 9, wherein the double slope cam comprises a plurality of drillings arranged in the body of the double slope cam, the drillings arranged so as to cooperate with two hollow axial pistons arranged axially on either side of the double slope cam during a delivery phase, so as to connect the cylinders in which the two hollow axial pistons slide through the double slope cam.
 12. The pumping device according to claim 11, wherein the hollow axial pistons each cooperate with one of the two inclined faces of the double slope cam via a hollow stud, the diameter of each hollow stud being greater than the distance separating two adjacent drillings.
 13. The pumping device according to claim 10, wherein the hydraulic pump has a housing comprising pipelines arranged to bring the cylinders of a first hollow axial piston into communication with the cylinders of a second hollow axial piston.
 14. The pumping device according to claim 7, wherein the hydraulic pump comprises a housing and the transfer pump comprises an upper pumping stage and a lower pumping stage extending respectively on either side of the hydraulic pump housing, each of the upper and lower pumping stages comprising pumping elements associated with a respective piston, the delivery pipelines opening into a common pipeline, and the suction pipelines of the lower pumping unit communicating with the common pipeline via a pipeline arranged along the casing of the hydraulic pump.
 15. The pumping device according to claim 7, wherein the pressure compensator comprises: a tube with an inner space communicating with the internal hydraulic circuit of the hydraulic pump and equipped with a base through which passes a drilling communicating with the lower zone; and a flexible separator or free piston counterheld by a spring and receiving firstly the pressure predominating in the drilling and secondly the pressure predominating in the internal hydraulic circuit of the hydraulic pump.
 16. The Pumping device according to claim 15, wherein the electric motor has a housing comprising firstly a cover through which passes a bore communicating with the inner space of the tube, and secondly a cap through which passes a bore communicating with the internal hydraulic circuit of the hydraulic pump.
 17. The pumping device according to claim 16, wherein the electric motor comprises a stator and a rotor carried by a motor shaft, the cover being provided with a bearing carrying one of the ends of the motor shaft, and the cap being provided with a bearing carrying the other end of the motor shaft, the motor shaft being connected to a shaft of the hydraulic pump carrying the double slope cam.
 18. The pumping device according to claim 7, wherein the seal is a compressible seal and the anchoring element comprises catches able to be spaced apart, the pumping device comprising a control mechanism for the seal and the anchoring element that is mobile between a released position and an engaged position, in which firstly the control mechanism axially compresses the seal such that when the pumping device is placed inside the casing, the seal is pressed radially against the inner wall of the casing, and secondly the control mechanism exerts a force on the anchoring element spacing the catches apart, such that when the pumping device is placed inside the casing, the catches come to rest against the inner wall of the casing.
 19. The pumping device according to claim 18, wherein the control mechanism is a hydraulic control mechanism and the pumping device comprises a hydropneumatic accumulator and a distributor linked to the hydropneumatic accumulator and to the hydraulic control mechanism, the distributor comprising a closed position in which communication between the hydropneumatic accumulator and the hydraulic control mechanism is interrupted, and an open position in which communication between the hydropneumatic accumulator and the hydraulic control mechanism is established, in order to move the control mechanism between its released position and its engaged position.
 20. The pumping device according to claim 19, wherein the hydraulic control mechanism is provided with a return means able to return the control mechanism to its released position, and is linked to the distributor such that the latter is able to move the control mechanism into its engaged position.
 21. The pumping device according to claim 19, wherein the hydraulic control mechanism is provided with a return means able to return and hold the hydraulic control mechanism in its engaged position, and is connected to the distributor such that the latter is able to move the control mechanism into its released position.
 22. The pumping device according to claim 18, wherein the control mechanism comprises a shaft carrying a guide piston and a cylinder mounted sliding on the guide piston against a spring.
 23. The pumping device according to claim 22, wherein the cylinder comprises a first moveable stop surface and the shaft comprises a second fixed stop surface, the anchoring element being a deformable liner mounted on the shaft between the first movable stop surface and the second fixed stop surface, the seal being mounted on the shaft between the first movable stop surface and the second fixed stop surface, the control mechanism comprising an intermediate element arranged between the seal and the anchoring element, the intermediate element comprising a flat surface facing the seal and a conical surface facing the deformable liner such that when the first movable stop surface is moved in the direction of the second fixed stop surface, the flat surface of the intermediate element compresses the seal and spaces the deformable liner from the anchoring element such that its catches are able to come into engagement against the inner wall of the casing. 